I'm having trouble getting data from a ResultSet object. Here is my code:
String sql = "SELECT type FROM node WHERE nid = ?";
PreparedStatement prep = conn.prepareStatement(sql);
int meetNID = Integer.parseInt(node.get(BoutField.field_meet_nid));
prep.setInt(1, meetNID);
ResultSet result = prep.executeQuery();
result.beforeFirst();
String foundType = result.getString(1);
if (! foundType.equals("meet")) {
throw new IllegalArgumentException(String.format("Node %d must be of type 'meet', but was %s", meetNID, foundType));
}
The error trace:
Exception in thread "main" java.sql.SQLException: Before start of result set
at com.mysql.jdbc.SQLError.createSQLException(SQLError.java:1072)
at com.mysql.jdbc.SQLError.createSQLException(SQLError.java:986)
at com.mysql.jdbc.SQLError.createSQLException(SQLError.java:981)
at com.mysql.jdbc.SQLError.createSQLException(SQLError.java:926)
at com.mysql.jdbc.ResultSetImpl.checkRowPos(ResultSetImpl.java:841)
at com.mysql.jdbc.ResultSetImpl.getStringInternal(ResultSetImpl.java:5656)
at com.mysql.jdbc.ResultSetImpl.getString(ResultSetImpl.java:5576)
at nth.cumf3.nodeImport.Validator.validate(Validator.java:43)
at nth.cumf3.nodeImport.Main.main(Main.java:38)
What am I doing wrong here?
Solution 1
Basically you are positioning the cursor before the first row and then requesting data. You need to move the cursor to the first row.
result.next();
String foundType = result.getString(1);
It is common to do this in an if statement or loop.
if(result.next()){
foundType = result.getString(1);
}
Solution 2
Every answer uses .next() or uses .beforeFirst() and then .next(). But why not this:
result.first();
So You just set the pointer to the first record and go from there. It's available since java 1.2 and I just wanted to mention this for anyone whose ResultSet exists of one specific record.
Solution 3
You have to do a result.next() before you can access the result. It's a very common idiom to do
ResultSet rs = stmt.executeQuery();
while (rs.next())
{
int foo = rs.getInt(1);
...
}
Solution 4
You have to call next() before you can start reading values from the first row. beforeFirst puts the cursor before the first row, so there's no data to read.
Solution 5
It's better if you create a class that has all the query methods, inclusively, in a different package, so instead of typing all the process in every class, you just call the method from that class.
Solution 6
You need to move the pointer to the first row, before asking for data:
result.beforeFirst();
result.next();
String foundType = result.getString(1);
